Just a week after upending the carefully planned schedule at the Republican National Convention in Tampa, Fla., with a hurricane, she appears to have set her sights on the gathering of Democrats here, where President Obama is set to accept the nomination in an open-air stadium on Thursday — with no umbrellas allowed.

As delegates began arriving Monday evening, the skies began darkening, with thunderstorms bringing the possibility of flooding to the Charlotte area. Weather forecasts suggested that storms might extend through Thursday night.

“We have an advisory team in place that is constantly updating a contingency plan in the event of severe weather, which will be announced if the need arises,” said Joanne Peters, a spokeswoman for the convention. Safety is a top priority, she said.

The political risk is high, just as it was for Republicans, who canceled the first day of their convention because of Hurricane Isaac. Democrats are eager to deliver their campaign message this week without the same kind of distractions.

On Monday, inaccurate rumors of a tornado warning circulated among the thousands of reporters at the Charlotte Convention Center. Convention planners, eager to believe that their long-scheduled events are less cursed than those of the Republicans were, quickly went to Twitter with a denial on behalf of the storm gods.

But even without the threat of a tornado, the weather appeared to be making every effort to be fair and balanced. Those gathered for a James Taylor concert Monday night found themselves drenched. Reporters who had planned a late arrival in Charlotte found themselves delayed by the storm.

“Dear Charlotte,” Chris Cillizza, the author of The Fix blog at The Washington Post, wrote on Twitter. “Please move the thunderstorms. Fix Force One is currently grounded.”

For now, the Democratic organizers appear unbowed by the prospect of a soggy conclusion to the convention.

“The convention proceedings at Bank of America Stadium will take place rain or shine, similar to other events at the stadium,” Ms. Peters said, noting that only extreme weather would force any changes in the schedule.

That may be fine for the millions of people who will watch Mr. Obama’s address on television. The president recently delivered one of his stump speeches in a downpour in Richmond, Va. — showing even more energy and enthusiasm than usual.

But that may be of little comfort to the tens of thousands gathered in the stadium.

A version of this article appears in print on 09/04/2012, on page A18 of the NewYork edition with the headline: Gray Skies Worry Democrats Eager for Smooth Convention.

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